Modifying LAMMPS / accessing variable from another fix

LAMMPS LAMMPS Mailing List Mirror
1

Dear LAMMPS users,

We recently introduced EChemDID to equilibrate voltage during reactive MD (by adjusting the electronegativity used for charge equilibration).
The method is detailed in the JCP http://aip.scitation.org/doi/10.1063/1.4927562
I am working on updating our code to make it more consistent with latest LAMMPS versions and also trying to keep LAMMPS’s code untouched.

I noticed a new variable (chizj) in the recent version of QEq which is set to zero by default and, added to the electronegativity (chi) then used to optimize charges.
I don’t know why this (chizj) variable has been introduced but it looks to me as a variable to include an external potential to the QEq?

I have a fix_echemdid that equilibrates the voltage and I was thinking using chizj to pass the external potential to the QEq.
This would allow echemdid to work directly with QEq regardless of the potential (as long as there is a potential consistent with QEq).
However, I have hard time to access the chizj variable from my fix_echemdid class.

I would like to know

  • if I am proceeding the right way. Does it make sense to use chizj to pass an external potential?
  • if yes, what is the best way to access chizj from my echemdid class?

Thank you,
Nicolas

www.polyu.edu.hk/80anniversary

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2

Dear LAMMPS users,

We recently introduced EChemDID to equilibrate voltage during reactive MD
(by adjusting the electronegativity used for charge equilibration).
The method is detailed in the JCP http://aip.scitation.org/
doi/10.1063/1.4927562
I am working on updating our code to make it more consistent with latest
LAMMPS versions and also trying to keep LAMMPS's code untouched.

I noticed a new variable (chizj) in the recent version of QEq which is set
to zero by default and, added to the electronegativity (chi) then used to
optimize charges.
I don't know why this (chizj) variable has been introduced but it looks to
me as a variable to include an external potential to the QEq?

​according to the source code management system, the chizj pointer has been
included in the QEQ package based class since its inception in ​september
2014.
also, it is set and used in fix qeq/slater. it is not at all present in fix
qeq/reax of the USER-REAXC package.

I have a fix_echemdid that equilibrates the voltage and I was thinking
using chizj to pass the external potential to the QEq.
This would allow echemdid to work directly with QEq regardless of the
potential (as long as there is a potential consistent with QEq).
However, I have hard time to access the chizj variable from my
fix_echemdid class.

I would like to know
- if I am proceeding the right way. Does it make sense to use chizj to
pass an external potential?

​no.​

- if yes, what is the best way to access chizj from my echemdid class?

​the common way in LAMMPS to expose internal data to other classes without
having to know its particular type ​is through adding an "extract()" method
to the class holding the data and adding the corresponding code to it.

axel.